Tardigrades could probably survive the otherwise complete annihilation of life on Earth

Blessed are the moss piglets: for they shall inherit the Earth.

Not everyone is familiar with the tardigrade (also known as the water bear, also known as the moss piglet, previously known as "animalcules"), and that's a damn shame. They're less than a millimeter long, sure, but they're almost certainly the most indestructible animals on the planet. You can expose them to the unforgiving vacuum of space, starve them for decades, dehydrate them for literally-who-knows-how-long, boil them, mash them, stick them in a stew, whatever, and as soon as you return them to normal conditions they'll perk right back up and go on their merry way. Their abilities are so obscenely awesome that some scientists are convinced they contain an unprecedented ratio of DNA that's "stolen" from other organisms by way of horizontal gene transfer, though these results proved controversial.

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How families across America are preparing for the apocalypse
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How families across America are preparing for the apocalypse
Jeff Nice empties his boot of dried corn at his farm in Kinston, North Carolina December 14, 2012. Preppers Jeff and Jeanie Nice live on a 13 acre farm where they raise beef, chicken, turkey and can vegetables from their garden. After completion of a government contact working in computers Jeff has spent most of his time on the farm tending to the livestock and general chores such as planting grass or keeping his equipment in working order. On the farm is a 200 yard rifle range where Jeff teaches hunter education and gun safety. Picture taken December 14, 2012. REUTERS/Chris Keane (UNITED STATES - Tags: SOCIETY AGRICULTURE)
Jeff Nice repairs a tractor disk at his farm in Kinston, North Carolina December 14, 2012. Preppers Jeff and Jeanie Nice live on a 13 acre farm where they raise beef, chicken, turkey and can vegetables from their garden. After completion of a government contact working in computers Jeff has spent most of his time on the farm tending to the livestock and general chores such as planting grass or keeping his equipment in working order. On the farm is a 200 yard rifle range where Jeff teaches hunter education and gun safety. Picture taken December 14, 2012. REUTERS/Chris Keane (UNITED STATES - Tags: SOCIETY AGRICULTURE)
A pen rests on a notepad with a list of chores at the Nice family farm in Kinston, North Carolina December 14, 2012. Preppers Jeff and Jeanie Nice live on a 13 acre farm where they raise beef, chicken, turkey and can vegetables from their garden. After completion of a government contact working in computers Jeff has spent most of his time on the farm tending to the livestock and general chores such as planting grass or keeping his equipment in working order. On the farm is a 200 yard rifle range where Jeff teaches hunter education and gun safety. Picture taken December 14, 2012. REUTERS/Chris Keane (UNITED STATES - Tags: SOCIETY AGRICULTURE)
Jeanie Nice trims excess meat off a cooked chicken to be used in soup in her kitchen in Kinston, North Carolina December 14, 2012. Preppers Jeff and Jeanie Nice live on a 13 acre farm where they raise beef, chicken, turkey and can vegetables from their garden. After completion of a government contact working in computers Jeff has spent most of his time on the farm tending to the livestock and general chores such as planting grass or keeping his equipment in working order. On the farm is a 200 yard rifle range where Jeff teaches hunter education and gun safety. Picture taken December 14, 2012. REUTERS/Chris Keane (UNITED STATES - Tags: SOCIETY ANIMALS FOOD)
Jeff Nice tends to his honey bees on his farm in Kinston, North Carolina December 14, 2012. Preppers Jeff and Jeanie Nice live on a 13 acre farm where they raise beef, chicken, turkey and can vegetables from their garden. After completion of a government contact working in computers Jeff has spent most of his time on the farm tending to the livestock and general chores such as planting grass or keeping his equipment in working order. On the farm is a 200 yard rifle range where Jeff teaches hunter education and gun safety. Picture taken December 14, 2012. REUTERS/Chris Keane (UNITED STATES - Tags: SOCIETY ANIMALS FOOD)
Chickens are seen in one of two freezers at the Nice family farm in Kinston, North Carolina December 14, 2012. Preppers Jeff and Jeanie Nice live on a 13 acre farm where they raise beef, chicken, turkey and can vegetables from their garden. After completion of a government contact working in computers Jeff has spent most of his time on the farm tending to the livestock and general chores such as planting grass or keeping his equipment in working order. On the farm is a 200 yard rifle range where Jeff teaches hunter education and gun safety. Picture taken December 14, 2012. REUTERS/Chris Keane (UNITED STATES - Tags: SOCIETY ANIMALS FOOD)
Jeanie Nice and her husband Jeff Nice carry parts for a shelving unit into their barn on their farm in Kinston, North Carolina December 14, 2012. Preppers Jeff and Jeanie Nice live on a 13 acre farm where they raise beef, chicken, turkey and can vegetables from their garden. After completion of a government contact working in computers Jeff has spent most of his time on the farm tending to the livestock and general chores such as planting grass or keeping his equipment in working order. On the farm is a 200 yard rifle range where Jeff teaches hunter education and gun safety. Picture taken December 14, 2012. REUTERS/Chris Keane (UNITED STATES - Tags: SOCIETY AGRICULTURE)
Phil Burns pulls a gun from his backpack full of survival supplies at his home in American Fork, Utah, December 14, 2012. While most "preppers" discount the Mayan calendar prophecy, many are preparing to be self-sufficient for threats like nuclear war, natural disaster, famine and economic collapse. Picture taken December 14, 2012. REUTERS/Jim Urquhart (UNITED STATES - Tags: SOCIETY)
Phil Burns, a firearms instructor, holds a handgun that he carries as part of his survival supplies at his home in American Fork, Utah, December 14, 2012. While most "preppers" discount the Mayan calendar prophecy many are preparing to be self-sufficient for threats like nuclear war, natural disaster, famine and economic collapse. REUTERS/Jim Urquhart (UNITED STATES - Tags: SOCIETY)
Phil Burns demonstrates the air purifying SCape Mask at his home in American Fork, Utah, December 14, 2012. While most "preppers" discount the Mayan calendar prophecy, many are preparing to be self-sufficient for threats like nuclear war, natural disaster, famine and economic collapse. Picture taken December 14, 2012. REUTERS/Jim Urquhart (UNITED STATES - Tags: SOCIETY)
Hugh Vail inventories his food storage at his home in Bountiful, Utah, December 10, 2012. While most "preppers" discount the Mayan calendar prophecy, many are preparing to be self-sufficient for threats like nuclear war, natural disaster, famine and economic collapse. Picture taken December 10, 2012. REUTERS/Jim Urquhart (UNITED STATES - Tags: SOCIETY FOOD)
Hugh Vail cuts firewood at his home in Bountiful, Utah, December 10, 2012. While most "preppers" discount the Mayan calendar prophecy, many are preparing to be self-sufficient for threats like nuclear war, natural disaster, famine and economic collapse. Picture taken December 10, 2012. REUTERS/Jim Urquhart (UNITED STATES - Tags: SOCIETY)
Mike Holland looks over as a chicken is run through the plucker after being slaughtered at the Holland family property in Warrenton, North Carolina December 13, 2012. Prepper Mike Holland lives with his wife, four children and three other men on their 13 acre property where they raise, chickens, turkey, goat and a cow for milk. In addition to livestock they also have a greenhouse and a few trailers that house food storage including multiple freezers. Outside of food preparations Holland has ammunition and firearms, a safe room, security cameras and a military grade generator for power. Picture taken December 13, 2012. REUTERS/Chris Keane (UNITED STATES - Tags: SOCIETY ANIMALS FOOD)
James Grant cuts a chicken's neck as he helps in the slaughter at the Holland family property in Warrenton, North Carolina December 13, 2012. Prepper Mike Holland lives with his wife, four children and three other men on their 13 acre property where they raise, chickens, turkey, goat and a cow for milk. In addition to livestock they also have a greenhouse and a few trailers that house food storage including multiple freezers. Outside of food preparations Holland has ammunition and firearms, a safe room, security cameras and a military grade generator for power.Picture taken December 13, 2012. REUTERS/Chris Keane (UNITED STATES - Tags: SOCIETY ANIMALS FOOD)
Mike Holland reviews his stock of dry food storage in a trailer at the Holland family property in Warrenton, North Carolina December 13, 2012. Prepper Mike Holland lives with his wife, four children and three other men on their 13 acre property where they raise, chickens, turkey, goat and a cow for milk. In addition to livestock they also have a greenhouse and a few trailers that house food storage including multiple freezers. Outside of food preparations Holland has ammunition and firearms, a safe room, security cameras and a military grade generator for power. Picture taken December 13, 2012. REUTERS/Chris Keane (UNITED STATES)
Noah Holland reads a book in the living room of his family's home at the Holland family property in Warrenton, North Carolina December 13, 2012. Prepper Mike Holland lives with his wife, four children and three other men on their 13 acre property where they raise, chickens, turkey, goat and a cow for milk. In addition to livestock they also have a greenhouse and a few trailers that house food storage including multiple freezers. Outside of food preparations Holland has ammunition and firearms, a safe room, security cameras and a military grade generator for power. Picture taken December 13, 2012. REUTERS/Chris Keane (UNITED STATES - Tags: SOCIETY)
James Blair cleans chickens at the Holland family property in Warrenton, North Carolina December 13, 2012. Prepper Mike Holland lives with his wife, four children and three other men on their 13 acre property where they raise, chickens, turkey, goat and a cow for milk. In addition to livestock they also have a greenhouse and a few trailers that house food storage including multiple freezers. Outside of food preparations Holland has ammunition and firearms, a safe room, security cameras and a military grade generator for power. Picture taken December 13, 2012. REUTERS/Chris Keane (UNITED STATES - Tags: SOCIETY ANIMALS FOOD)
A knife is covered with blood and a few feathers while it is used to slaughter chickens at the Holland family property in Warrenton, North Carolina December 13, 2012. Prepper Mike Holland lives with his wife, four children and three other men on their 13 acre property where they raise, chickens, turkey, goat and a cow for milk. In addition to livestock they also have a greenhouse and a few trailers that house food storage including multiple freezers. Outside of food preparations Holland has ammunition and firearms, a safe room, security cameras and a military grade generator for power. Picture taken December 13, 2012. REUTERS/Chris Keane (UNITED STATES - Tags: SOCIETY ANIMALS)
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Now, scientists have taken the logical next step and tried to figure out just how much a tardigrade might survive. Their study came out Friday in the journal Scientific Reports, and results suggest that there probably isn't a single cosmic cataclysm that could wipe out all the snurfly-nosed lil moss piglets on the planet.

Even if you love tardigrades as much as we do, a study on their post-apocalyptic fates might seem a little wasteful. But it makes a lot of sense if you stop to think about it: we know that tardigrades can survive basically anything that we can throw at them, to an extent we don't see with any other animal. So for researchers who want to understand how hard it would be to wipe out all life on Earth in one go, the water bear makes a great mile marker: if these eight-legged swimmers don't make it through a natural disaster, nothing else stands a chance—in the animal kingdom, anyway. Microbes are a different question entirely.

Asking that question is about more than figuring out the odds of Earth's survival. What the researchers are really trying to figure out is how likely it would be for life to evolve on another planet but get wiped out before we had the chance to find it. Space is big and time is long, so it wouldn't be surprising if our first encounter with a planet with the evolutionary potential to host life happened at a less-than-ideal point in that world's history. Take Mars, for example: some scientists hold out hope that this relatively Earth-y rock teemed with microbial life billions of years ago, before its atmosphere slipped away into space. But how likely is that sort of thing? When life does evolve (assuming it's happened more than once, which is unfortunately still an open question), does it tend to stick around?

Based on the humble moss piglet, scientists from Oxford and Harvard say it does. They calculated the risks posed to tardigrades' marine habitats by asteroids (conclusion: nothing big enough to totally boil up our oceans should ever intersect with Earth's orbit), supernovas (conclusion: the probability of a star explosion massive and close enough to totally boil up our oceans happening during our Sun's lifetime is "negligible"), and gamma-ray bursts (conclusion: again, the probability of this even-more-powerful-but-even-more-rare stellar explosion happening in close enough proximity to boil up our oceans is "minor").

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In other words, water bears are in it for the long haul. Like, until-the-Sun-sterilizes-the-entire-planet long. Unfortunately, even these resilient critters won't survive once our host star ages into a bigger, hotter thing than it is now. The Sun should be around for about another 5 billion years, but most estimate that it will turn ocean-boiling hot in about 1 billion years. Until then, though, we know the animal kingdom's foothold on the planet is secured—by eight very tiny feet.

"A lot of previous work has focused on 'doomsday' scenarios on Earth—astrophysical events like supernovae that could wipe out the human race," David Sloan, co-author and physics researcher at Oxford University, said in a statement. "Our study instead considered the hardiest species—the tardigrade. As we are now entering a stage of astronomy where we have seen exoplanets and are hoping to soon perform spectroscopy, looking for signatures of life, we should try to see just how fragile this hardiest life is. To our surprise we found that although nearby supernovae or large asteroid impacts would be catastrophic for people, tardigrades could be unaffected. Therefore it seems that life, once it gets going, is hard to wipe out entirely. Huge numbers of species, or even entire genera may become extinct, but life as a whole will go on."

Of course, with a sample size of one, scientists can't be sure that every planet capable of hosting life will create a creature as utterly indestructible as the tardigrade. They could be just as special in the galaxy as they are on our own planet.

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